stix Posted May 5, 2016 Posted May 5, 2016 I'm sure at some point I had this written down, but can't find. I spent almost an hour on goggle but I couldn't find anything definitive. I'm aware of the changing thrust profile due the geometry of the fuel grain (similar to a finocyl shape, I believe?). So just an "average" burn rate would be useful to know. I'm hoping someone on this forum will have a rough idea - doesn't need to be exact. cheers.
lloyd Posted May 5, 2016 Posted May 5, 2016 500,000 Kg in about 255 seconds, so about 1958.5 kg/sec If you know the dimensions, you can determine the linear rate. LLoyd
stix Posted May 5, 2016 Author Posted May 5, 2016 Yeah thanks LLoyd. No easy answer? - you're going to force me to do the math aren't you? The weight of fuel burnt over time is irrelevant to my question, as you well know. Yes, if I knew the dimensions, and the total burn time - then I could work it out. I'm being lazy.
FlaMtnBkr Posted May 5, 2016 Posted May 5, 2016 Wouldn't Lloyd's answer be "just an average burn rate"?
lloyd Posted May 5, 2016 Posted May 5, 2016 Yup... the linear rate varies over time, being caused to do so deliberately by the shape of the fuel grain. They want different thrust at different gross weights in order to achieve more-or-less constant acceleration. LLoyd
stix Posted May 5, 2016 Author Posted May 5, 2016 Wouldn't Lloyd's answer be "just an average burn rate"? Yes, that would be the case - that's all I was asking. Yup... the linear rate varies over time, being caused to do so deliberately by the shape of the fuel grain. They want different thrust at different gross weights in order to achieve more-or-less constant acceleration. LLoyd Yes LLoyd, thank you. It's ok, I'll work it out the hard way if required. Seems like I may be able to get hold of a surplus SRB via the black market. I'd rather not though - not just because of the expense, but the neighbours are probably getting sick of my "back yard" rocket motor tests. I'll check it out again and write down the info this time. I think the measurements ie. web thickness and total burn times are given on one of the websites I looked at - I'll work it out.
MadMat Posted May 5, 2016 Posted May 5, 2016 Ewww,If your calculating out changes in burn rates to achieve constant acceleration, that sounds like calculus. have fun.
lloyd Posted May 5, 2016 Posted May 5, 2016 Sounds a WHOLE lot like The Calculus, Mat! Indeed! Integrations, summations, differentiations!!! All fun! Hmmm... It's been a while since I did any of that by hand... computers are so much faster and easier. Maybe I need to break out some graph paper and see if I remember ANY of it! <G> Y'know... funny story... (well, I think it's funny). When I was in my first two years of Jr. College, I took (and flunked ... well... dropped out of) The Calculus. I had been on a technical flight path, but a counselor convinced me that since the moon flight program was soon to be over, we just didn't need any more 'hard science' engineers -- the market would be glutted with them, all looking for jobs. So... I should go into business management. And The Calculus just seemed like it was pretty well useless to me in that endeavor. 40 years later, AS A BUSINESS MANAGER, I needed it, again! DANG! It took me a while to find the tools to do what I had never really learned to do by head and hand. Since then, I've learnt enough of it to get me by, and there's so much on-line in the way of solutions and tools, that unless you're a theoretical physicist or a rocket scientist, you just don't really need to KNOW The Calculus anymore. Oops! Wait! We ARE rocket scientists!!!! ARRRGHHH! Lloyd
Mumbles Posted May 5, 2016 Posted May 5, 2016 Not meaning to take this even farther down the rabbit hole, but MIT offers a huge selection of online courses should anyone need a refresher or resource to learn calculus. http://ocw.mit.edu/courses/ 1
MadMat Posted May 5, 2016 Posted May 5, 2016 (edited) I still got my old textbooks and a TI-84 Edited May 5, 2016 by MadMat
lloyd Posted May 5, 2016 Posted May 5, 2016 Actually... my go-to calculator is a TI-30X IIS, being a 'full scientific' with some reasonable programming capabilities, too. You cannot get them anymore, except used, so my back up is a CASIO Fx115 ES Plus, which perverts everything the Ti does, but at least can DO the same things! <G> LLoyd
pyrokid Posted May 6, 2016 Posted May 6, 2016 (edited) Lloyd, are you sure you're not confusing the TI30xIIS with a different one? http://www.amazon.com/Texas-Instruments-Scientific-Calculator-Accents/dp/B00000JBNX Everyone I know hates these because the buttons are terrible and you waste time with messed up entries. Edited May 6, 2016 by pyrokid
AzoMittle Posted May 6, 2016 Posted May 6, 2016 (edited) I pulled the following from a table (this is just an excerpt) from Rocket Propulsion Elements (8th edition) by George P. Sutton and Oscar Biblarz. If you need me to find specific equations, methods, or data let me know and I'll see what I can do. Out of curiosity, what do you plan to use this info for? Vehicle: Delta IVDesignation Propulsion System: RS-68Stage: 1Number of Propulsion Systems per Stage: 1 or 3Thrust lbf/kN per Engine/Motor: Full Power 750,000/3.341 (Vacuum) 655,000/2.91 (Sea Level)Specific Impulse (sec): 409 (Vacuum) 364 (Sea Level)Mixture Ratio, Oxidizer to Fuel Flow: 6.0Champer Pressure (psia): 1410Nozzle Exit Area Ratio: 21.5:1Inert Propulsion Mass klb/kg: 14,200/6,455Vehicle: Delta IVDesignation Propulsion System: RL 10B-2Stage: 2Number of Propulsion Systems per Stage: 1Thrust lbf/kN per Engine/Motor: 24,750/0.110Specific Impulse (sec): 465.5 (Vacuum)Mixture Ratio, Oxidizer to Fuel Flow: 5.88Champer Pressure (psia): 633Nozzle Exit Area Ratio: 285:1Inert Propulsion Mass klb/kg: 664Vehicle: Shuttle Orbiter Propulsion System (Number of Units): Space Shuttle Main Engine (3) Number of Starts and Typical Burn Time: Start at launch 8.4 min duration; Life: 55 starts and 7.5 hr Propellant and Specific Impulse (Is): Liquid hydrogen-Liquid oxygen, 4464 N-sec/kg (455 sec) Thrust: 1670 kN each (375,000 lb) (Sea Level), 2100 kN each (470,000 lbf) (Vacuum), Throttled 109 to 65% of rated power Mission: Lift orbiter off ground and accelerate to orbit velocity. Individual engines can be shut down to reduce thrust level. Vehicle: Shuttle Orbiter Propulsion System (Number of Units): Orbital Maneuver Systems (2) Number of Starts and Typical Burn Time: S3 to starts/mission; designed for 1000 starts, 100 flights, 15 hr of cumulative time Propellant and Specific Impulse (Is): Monomethylhydrazine (MMH) and Nitrogen tetroxide (NTO), Is = 313 sec Thrust: Two orbiter maneuver, engines; 27 kN each (6000 lbf) (Vacuum) Mission: Insert orbiter vehicle into Earth orbit, correct orbit, abort, and deorbit maneuver Vehicle: Shuttle Orbiter, Solid Rocket Boosters (SRBs) Original Version Propulsion System (Number of Units): Attached to the external tank; multisection (2) Number of Starts and Typical Burn Time: Single start at launch 2 min Propellant and Specific Impulse (Is): 70% Ammonium perchlorate, 16% Aluminum, 12% Polybutadiene Acrylic Acid Binder, 2% epoxy curing agent; Is = 292 sec Thrust: 14,700 kN each, or 3.3 x 106 lbf each Mission: Boost Shuttle vehicle to about 5,500 km/hr Vehicle: Shuttle Orbiter, Solid Rocket Boosters (SRBs) Original VersionPropulsion System (Number of Units): Seperation rocket motors (16)Number of Starts and Typical Burn Time: 4 each at forward frustum and aft skirt; 0.66 sec nominalPropellant and Specific Impulse (Is): Solid propellant; Is = 250 secThrust: 97,840 N each or 22,000 lbfMission: Move SRB away from vehicle after cut-off It also says the following, At the time of this writing (early 2008) for this new 8th edition National Aeronautics and Space Administration (NASA) had awarded the initial contracts for a new large manned space flight vehicle identified as Ares I. It is intended to replace the aging Space Shuttle after about 2012. It is planned to use a large single 5-segment solid rocket motor as booster propulsion (being developed by ATK Launch Systems) and the second stage will use a J-2X liquid propellant rocket engine with LOX/LH2 propellants (being developed by Pratt & Whitney Rocketdyne). Edited May 6, 2016 by AzoMittle
lloyd Posted May 6, 2016 Posted May 6, 2016 Kid,"TI3xIIS"?? I've never heard of that model, mine is the TI-30X IIS... just like the one you show in the link. Mine is a bit older than the one depicted there, but that's the model. I have no idea what you mean by "the buttons are terrible". Mine work perfectly well, and it's been about as abused as a calculator could be and still function at all. Your "everyone you know" appraisal doesn't seem to be shared by the scientific and technical community. According to every metric I've seen, the TI-30X series is always among the top 10 best-selling scientific calculators ever made. I love it. For a 'personal' calculator, that's really all that matters. When I really have a need to express myself in RPN, I switch over to my old HP! <G> LLoyd
FlaMtnBkr Posted May 6, 2016 Posted May 6, 2016 The Ti-83 graphing calculator was always the recommended calculator for all my math, science, and engineering classes. Anyone know if the Ti-84 is the predecessor? That was before smart phones and when an ok laptop was $2k+ (with 4-6 gb hard drives being common and a random 8 gb in the high end, and ram measured in mb). I would imagine they have some great calculators now with beautiful displays, expandable memory, and WiFi to grab programs and exchange data. At least I would think so but maybe tablets play that role?
Mumbles Posted May 6, 2016 Posted May 6, 2016 Functionally the 83 and 84 are nearly identical. The 84 is basically the 83 with upgraded processing power and memory, some physical redesign, and more modern connectivity. Supposedly the 84 comes with more preloaded programs and functionality, and has some screen improvements. The 83/84 has been the standard for the last 20 years. This is good and bad. It's good to have a familiar and uniform platform, which has now been included into text books and can really be integrated into the curriculum. This comes with the downside that they basically have a monopoly now which allows them to still charge ca. $100 for a new calculator with no real technological improvements for two decades. Don't get me wrong, the functionality is great, but it's overpriced for technology that can be accomplished with a cell phone app now. I have some friends who are math teachers, and there's been a growing movement to get away from the TI calculators. It prices out some lower income schools, they're commonly stolen, and like I said they're kind of ancient. There are programs and applications that mimic the interface and functionality available for free to very inexpensively. 1
stix Posted May 8, 2016 Author Posted May 8, 2016 As much as I like to reminisce about old time calculators, it doesn't really answer my basic question. But just to go along with it for a moment... I had a TI calculator many years back that had multiple memory areas that you could store mini-programs. I used it to calculate the altitude of small 2 stage rockets. I don't remember what model it was, but I loved it. Then I bought an IBM XT Computer. The calculated results were then tested using a "real" 2 stage rocket and a home-made theodolite consisting of a tube, two cross-hairs and a protractor glued to the bottom. Although not using triangulation, the results proved useful - and fun . . . Out of curiosity, what do you plan to use this info for? Well Azo, that is THE question. I've got some ideas regarding "scaling" of rocket motors. This thread is a pre-cursor to that. The now defunct shuttle SRB's seem like a useful comparison. I was hoping that somebody on this forum would have an idea of the burn rate. Not exact, but a rough approximation would do. Unfortunately none of the info provided thus far is very useful.
BlueComet24 Posted May 8, 2016 Posted May 8, 2016 I don't want to drag this thread too far off-topic, but I thought I'd mention WolframAlpha.com. It's tremendously useful for math, including calculus. You can enter things like d/dx[f(x)] and it'll tell you the derivative of f(x) (replaced with your function, of course) or int_a^b f(x) for the integral from a to b.
lloyd Posted May 8, 2016 Posted May 8, 2016 Unfortunately (for us 'pretending cerebral types'), anything you can do by 'rules' of math, rules of The Calculus, or rules of any other discipline, can be done by sophisticated software. I'm tickled to death that The Calculus is now possible by computer, because I never mastered even the trig, much less the whole discipline! (actually, I went back and LEARNED the trig, because I was pissed at myself for not doing it earlier... but it's not the same.... <G>) Lloyd 1
Nessalco Posted May 9, 2016 Posted May 9, 2016 If you want to know about rockets, head over to The Rocketry Forum. There are rocket scientists over there, and many folks compound their own propellants. The SRB propellant is known and (I think) pretty well characterized. Kevin 1
dagabu Posted May 9, 2016 Posted May 9, 2016 If you want to know about rockets, head over to The Rocketry Forum. There are rocket scientists over there, and many folks compound their own propellants. The SRB propellant is known and (I think) pretty well characterized. Kevin True that but dont mention pyro, they are a sensitive bunch over there....
Nessalco Posted May 9, 2016 Posted May 9, 2016 I'll respectfully disagree, Dave. I live in both worlds, as do other rocketeers. I talk about my pyro interests a lot - though I had to eat a healthy serving of crow after recommending a certain pyro vendor for an 'unobtanium' grade of ammonium perchlorate, and he robbed some of them, too. The hybrid crew (solid fuel, liquid oxidizer) do a lot of work with pyro chemistry, striving for that 'ultimate' fuel. I'll agree there have been some historic differences, mostly at the level of the NFPA. Water under the bridge, IMHO. KO
dagabu Posted May 9, 2016 Posted May 9, 2016 I am happy that you haven't been flamed by them yet. It was a few years back for me and once I dropped the pyro part, they were fine.
stix Posted May 10, 2016 Author Posted May 10, 2016 If you want to know about rockets, head over to The Rocketry Forum. There are rocket scientists over there, and many folks compound their own propellants. The SRB propellant is known and (I think) pretty well characterized. Kevin Thanks for the suggestions Kevin and Dave. I tend to use this forum as my "go to" for most things. I did sign up to the Rocketry Forum some time back. The info there is great. However, the section of particular interest to me is under [RESTRICTED] Research. TRF now hosts a restricted forum related to Research Motors. Requirements for access are: 1) NAR or TRA senior member2) US Person (US Citizen or US Permanent Resident (Green Card Holder))3) High Power Certification (Level 1, 2 or 3) Fair enough. Unfortunately for me, I don't qualify. I can understand the reasons for it, so all good. The composition of the SRB's fuel is well documented. The burn rate is not - the reality is that this is not an actual requirement for my testing!! - I just thought that it was an easier question to ask, and may have been known by a few members of this forum. I could/should have titled this thread "APCP - Approx. Burn Rate - Any Ideas?" I can see how anyone mentioning "scale-up theory" and APCP could be viewed in a negative light. From what I've read, the scaling of solid fuel rocket motors is a point of interest and not a known quantity even to professionals - "Real" Rocket Scientists. I'm certainly not saying that I'm going to solve "Scale-up-theory" but it has always been of interest to me since I first ground up some bought gun powder and rammed it into a tube (some 30+ yrs back). Cheers.
FlaMtnBkr Posted May 16, 2016 Posted May 16, 2016 If you aren't looking for a rough kg/s answer what are you looking for? Forgive my ignorance. Are you looking for an actual equation or graph that describes the amount of fuel burned with time? That seems a bit more than a rough estimate. I'm just curious though and have never studied rocket motor design so I may be missing something very basic.
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